The present invention relates to fire-fighting equipment, and more particularly to a monitor or water cannon that can be aimed in any direction and at any elevational angle. The invention specifically relates to a system for accommodating wiring to electrical components mounted on the rotating monitor.
In fire fighting, water cannons or monitors are used to direct a stream of water onto a specific location. Monitors can be mounted on a fire truck or on an aerial ladder assembly—anywhere that allows the monitor to accurately direct the water stream. The typical modern monitor permits adjustment of the elevational angle of the monitor nozzle to vary the distance over which the stream is directed. In addition, the monitor can be rotated in a horizontal plane so that the water stream can be precisely positioned regardless of the location and orientation of the fire truck of aerial ladder.
In many water cannons or monitors, the elevational and rotational adjustments are made manually, such as by rotating handwheels associated with the monitor. Monitors have now evolved to permit remote control of the elevational and rotational positions of the monitor nozzle. This remote control is necessary where manual operation of handwheels is problematic. A remote control monitor is particularly advantageous for a monitor mounted to an aerial ladder. Remote control allows truck mounting of a monitor at a location that would be otherwise inaccessible or hazardous to the fire fighter for manual operation.
The typical remote control system utilizes electric motors to drive gears for rotating the monitor in lieu of the handwheels. The motors are most typically powered off the vehicle electrical system, which means that electrical cables extend from the monitor to an electrical junction. In addition, many remote control systems include a control box connected to the monitor by a long electrical cable. At least some of the electrical components of the monitor are mounted on the rotating body of the monitor. Consequently, the remote control monitors require some means for providing power and communication to the rotating electrical components.
One typical means for interfacing with the rotating electrical components is through a number of electrical conducting slip rings. The slip rings maintain electrical contact between rotating components through sliding contact between a ring and brushes, or between stationary and floating contacts. One problem posed by the slip ring system is that individual slip ring arrangements are required for each electrical connection. For instance, if the monitor includes two motors and two control circuits for those motors, two slip ring arrangements are needed to provide power to each motor and two slip ring arrangements are required to provide control signals to the control circuits. Alternatively, a single power slip ring can be used to provide power to each motor.
In yet another alternative, the control signals are transmitted wirelessly, thereby eliminating the need for multiple slip rings. However, wireless transmission requires that rotating body of the monitor carry a receiver, which increases the cost and complexity of the monitor. Moreover, care must be taken to ensure that avoid interference between the monitor control transmissions and other wireless signals being transmitted at the scene of the fire. Some monitors include position sensors that provide verification of the vertical and rotational position of the monitor nozzle. The wireless approach thus requires a transmitter on the monitor, which again increases the cost and complexity of the system.
One significant drawback of the slip ring system is that the metallic conductors are prone to corrosion. This problem is exacerbated because the monitor is by its very nature used in a wet environment. Water within the slip rings not only speeds up corrosion, it also disrupts the electrical contact between the slip ring components.
A wiring system is needed for the electrical components of a rotating monitor or water cannon that eliminates these problems with the slip ring approach. This wiring system must not be compromised even by direct contact with water. In addition, the wiring system must accommodate the horizontal plane rotation between the base and rotating body of the water monitor. Most optimally, this rotation is at least 180° in either direction from a neutral position so that the water monitor can provide the maximum coverage area.